One of the significant requirements in a complex biological sample/mixture analysis, proteomics and other omics applications is the need to pre-process highly complex mixtures of molecules prior to mass spectrometry (MS) analysis. By coupling ion mobility spectrometry (IMS) to MS, gas phase separation of the mixture is achieved using ionic mobility differences and also an orthogonal dimension of analysis can be obtained.
However, the peak separation or resolving power of a given IMS device to separate two components of the mixture is limited by the fact that the ionic species diffuse with time. While ions drift over a long drift section of a mobility device, they separate out based on their mobilities. However individual peaks also broaden due to diffusion.
The increasing plume thickness with increasing time, if curtailed, would increase the separation characteristics significantly. The problem being addressed is to periodically bunch individual ion mobilities into tighter ion packets, while maintaining the time separation (resolution) between other ion packets (mobilities).